Parasiticide and method of preparing same



Patented Feb. 20, 19402 PARASITICIDE AND METHOD or PBEPABINGSAME Robert H. Daines, Jr.,- Highland Park, N. 1., as-

signor to Endowment Foundation, New Bruns- I wick, N. J., a corporation of New Jersey No Drawing.

'1 Claims.

value in protecting the host against invasion by microorganisms. In certain soils, however, mercury salts have consistently given unsatisfactory protection to the plants ,where protection was desired, either when used as a soil treatment or as a dip for underground plant parts.

As far as I am aware, the'metallic mercury mixtures which have been used in the past have simply been prepared by mixing metallic mercury with a diluent, or else they have been prepared chemically by simply mixing a mercury saltwith an alkaline material, such as some form of lime, the result otwhich is a precipitate of mercuric oxide on the alkaline diluent. This mercuric oxide is further reduced to metallic mercury by the addition of some appropriate reducing agent, after which the product is filtered undesirability of the carrier being alkaline in nature will be made clear by the following: Inorganic soil colloids have the power of-uniting chemically with cations. This union is loose and unstable in the cases of hydrogen, sodium, etc., but much more firm in.the case of mercury. The amounts of the cations bound in this manner vary with the pH of the system, the quantity increasing rapidly as the system becomes more alkaline. To illustrate, a 25 gram sample of a sassafras loam at a pH of' 6.5, bound and held against leaching with 2004:. c. of water, three times as .much mercury as did a comparable sample of soil at a pH of 4.9.

when metallic mercury is mixed n a soil, there is a tendency for some of the ercury to go into solution. As the mercury goes into solution it is bound by the system. This procedure is continued until the system in the immediate vicinity of the metallic mercury particle is saturated with mercury, whereupon an equilibrium is established after which the amount of metallic Application July 25, 1935, Serial No. 33,101

off and dried for use as a dust. However, in this mercury is not reduced by its going into solu-* tion; or the metallic mercury particle goes completely into solution and is bound by the system. In the first case, the metallic mercury remaining as such after the system becomes saturated with 5 soluble mercury, is available for vaporization and hence can exercise its fungicidal powers at a considerable distance by penetrating the soil in the vapor form. In the second example given above, the metallic mercury is not available for vapori- 10 zation because it has gone into solution and bound locally by the system.

Where metallic mercury is deposited on an alkaline carrier, the soil in the immediate vicinity is made more alkaline than where the carrier 1 .is neutral. The alkalies required for the chemical method of depositing metallic mercury on a carrier'would very likely make the soil immediately surrounding them even more alkaline than pH 7.0. This being the case, the capacity of the 2 soil for binding the soluble mercury phase would be greatly increased, which in turn would decrease the amount of mercury remaining in the metallic state, which in turn would decrease the effectiveness of the fungicide. 25

After much experimentation with the various salts of mercury, I have come to the conclusion that metallic mercury furnishes the vapor that migrates and contributes to killing the fungus growth. In addition, it should be noted that the 80 vapor pressure of metallic mercury is higher than is the. vapor pressure of any other known inorganic mercury compound.

The problem then is to produce a mercurial in which the mercury is present as metallic merso cury. From my experiments Ihave also determined that to get the best results, mercury should be used in a very fine state, and in the manner ,to be hereinafter set forth, and which is distinctly different from any other process of which 40 I am aware. L

The finished paraslticide product herein specifically claimed should have suitable physical properties to enable it to be used as a soil treatment as heretofore pointed out.

In my development work, I secured mo'st excellent results by preparing parasiticide in the following manner:

'Metalllc mercury was placed in a suitable heating vessel, such as an Erlenmeyer container, through the stopper of which an air tube extends a lo some point over the mercury. A T-shaped ube has one arm extending through the stopper of the container, while another arm extends I into a receptacle, the stem of the T going through the stopper of another vessel, within which is 1 placed a carrier in a dust form. Connected to to differences in temperature, the mercury vapors, in the form of very small globules, are deposited on the carrier and transmitted into the receiving chamber. By this method'a mixture of metallic-mercury, with any desired carrier, can be made, provided only that the carrier is capable of being dusted or sprayed. Therefore my new method of preparing the parasiticide or dip is a decided improvement in every way over any method so far proposed, or of which I am aware.

With this process, it is thus possible to select carriers which possess the desired physical properties best suited for the use for which they are intended. For example, when the parasiticide is to be used as a dust for seeds, a carrier that.

has high adhesive properties to the particular seed treated should be used. When the parasiticide is to be used only as a dip, the carrier should possess lyophilicproperties such as bentonite. When the parasiticide is to be used as a soil treatment, the carrier can be most anything, as long as the mercury is in a finely divided state, as indicated above. For example, talc nothaving much 'afiinity for water and which does not form lumps readily, may be mixed with a fertilizer for treatment of some soils. When the soil ,has high oxidizing properties, a metal higher than mercury in the electro-motive series is highly essential for reasons which will belater pointed out.

The chemical methods which have been used in the past for the' production of a mixture of metallic mercury and a diluent, depend on the carrier being alkaline enough to form the oxide of mercury when it comes in contact with a mercury salt. This limits the. diluents to a group of alkaline materials, such as calcium lime, mag-'- nesium lime, etc., which do not have pronounced lyophilic properties. Due to their lack of lyophilic properties, they do not form around themselves, a water shell sufiicient to be of much use.

This lack of affinity for the solvent causes them to settle to the bottom rapidly, which property is very undesirable in a plant part dip.

In the many tests that I have made, I have found that a fungicide prepared as heretofore described, and used in the soil in a similar manner to other materials, including mercury compounds, is far superior and much more effective in controlling Rhizoctonla, a fungous growth that attacks potato plants, than fungicides heretofore used. The reason for this greater effectiveness, I believe to be because the mercury is in a finely divided form, whereby the chemically unreactive mercury volatilizes, and the vapors penetrate the soil to a considerable distance, so that the protective action is available at ,a considerable distance from the point ofapplication; whereas in the past the methods used to produce a parasiticide containing metallic mercury, as has been pointed out, have not been such that the mercury could be uniformly mixed, or when uniformly mixed, an undesirable alkaline diluent has been required. When the salts of mercury are used, these are in many cases dissipated in the soil without being converted into metallic mercury, which is the vapor giving substance. 7

For use in soils which have an oxidation potential high enough ,toconvert part or all of the metallic mercury into a soluble state before the critical disease period arrives, a carrier should be used which has the power of converting the soluble mercury back into the insoluble metal. Such carriers are:

Magnesium Nickel Aluminum Tin Manganese Lead Zinc Copper u Cadmium Bismuth Iron Antimony which have the'power of doing this to a greater or lesser degree; that is to say, one metal higher than another in the above series has a greater tendency to go into solution than one below it; or, stated in another way, a metal listed first above another will be completely dissolved before a following metal in the list is much afiected. However, after the first metal goes into solution, the second metal may also become soluble. Thus, if the metal zinc and a mercury salt be mixed together and applied to the soil, a reaction takes place which produces zinc salt and metallic mercury, which will then give off its vapors to destroy the fungous growth on the plant.

I have secured excellent results with zinc because it is easily dusted, in addition to being relatively cheap and light, and does not possess great toxic properties itself.

v Copper, in some respects, is even better than zinc,'because it does not go into solution as easily claims, the word carrier is to be considered as composed of one or more materials.

From what has been said, it will be seen that the details for carrying out my invention, may va over a considerable range without departing from the spirit of the invention orthe scope of the appended claims.

What I claim is:

1. A parasiticide for controlling plant parasites in or on the soil including mercuryv and a carrier in a relatively finely divided state including at least one metal in the electro-motive series above metallic mercury.

A parasiticide for controlling plant parasites in or on the soil including mercury and a metallic carrier in a relatively finely divided state for said mercury, the carrier being higher in the electro-motive series than mercury.

3- A parasiticide for controlling seed and plant diseases substantially in the manner described including metallic mercury and a carrier comprising at least one metal higher in the electromotive series than metallic mercury and in a relatively finely divided solid state.

4. The method of preparing a parasiticide for the control of seed and plant parasites which consists in putting metallic mercury into a vescarrier higher in theelectro-motive series than carrier into another vessel, connecting both vessels to a common discharge member and forcing, as by a stream of air, the mercury vapor and the powdered carrier into said common member whereby flne particles oi metallic mercury are deposited on the powdered particles of said carrier.

5. The method or preparing a parasiticlde for the control of seed and plant parasites which consists in heating metallic mercury to cause it to pass into a vapor, then passing this vapor into contact with fine sub-divisions of a metallic metallic mercury.

6. The method of preparing a parasiticide for the control of seed and plant parasites which consists in heating metallic mercury to cause it to pass into a vapor, then passing this'vapcr into contact with fine sub-divisions of a carrier containing at least one metal, in the electromotive series above metallic mercury.

'7. The method of preparing a parasiticide for application to. the soil in the manner described for the control of seed and plant parasites, which consists in making an intimate union between at least one metal in a relatively finely divided state higher in the electro-motive series than metallic mercury, and metallic mercury, said one metal acting to decrease the soluble phase of the mercury.

, ROBERT E. DAINES. Jr. 

